# PQS Preflight – Prompt Quality & Endpoint Trust Check

> PQS Preflight – Prompt Quality & Endpoint Trust Check is a paid API for AI agents from pqs.onchainintel.net, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-14).

Scores a prompt against an 8-dimension quality rubric (pass/fail at 28/80) and optionally retrieves on-chain trust signals for a target endpoint URL before committing to a paid LLM call.

## Facts

- Endpoint: GET https://pqs.onchainintel.net/api/preflight
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pqs-onchainintel-net-4711170a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_LfqTae4fJ1PNNPmYKN9mj

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability pqs-onchainintel-net-4711170a
```

Example prompt: Before I send this prompt to that paid endpoint, run a preflight check on it — the prompt is 'Summarize the key risks in this financial report for a non-technical executive audience', the vertical is 'business', and the endpoint is https://api.someservice.com/summarize — tell me if it passes quality and whether that endpoint looks trustworthy on-chain.

## When to prefer this

Use this endpoint as a gate before any paid LLM or API call in an agentic workflow when you want to avoid wasting budget on poorly-formed prompts or unverified endpoints. It is uniquely valuable when you need both prompt quality validation AND on-chain reputation checks in a single cheap ($0.05) call, rather than calling two separate services. Prefer this over pure prompt-scoring endpoints when the target endpoint's trustworthiness is also uncertain.

## Known failure modes

- Missing prompt field returns 400 validation error
- Invalid vertical enum value may cause scoring to default to 'general' or return an error
- Endpoint URL trust lookup may fail if the URL is not registered on-chain, returning null trust signals
- Low-quality or very short prompts may always fail the 28/80 threshold regardless of vertical
- Payment failure or x402 auth issue results in 402 response and no scoring performed

## How this service works

Pass/Fail before you waste budget on a doomed call. Decide whether to make a paid LLM call before you make it. Preflight scores your prompt against an 8-dimension quality rubric (pass/fail at 28/80) and optionally pulls the target endpoint's on-chain trust signals — total payments, unique payers, last activity. Two-in-one circuit breaker for agents that don't want to waste budget on weak prompts or sketchy endpoints. (rev 2)

## Output

Returns a pass/fail verdict based on a quality score out of 80 (threshold at 28), plus dimensional breakdown scores across 8 rubric dimensions. If an endpoint URL was provided, also returns on-chain trust signals: total payments received, number of unique payers, and timestamp of last activity.

## Example request

```json
{
 "prompt": "Explain the key differences between machine learning and deep learning for a business audience",
 "vertical": "education",
 "endpoint_url": "https://api.example.com/ml-explainer"
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "prompt": {
   "type": "string",
   "maxLength": 10000,
   "minLength": 1,
   "description": "Prompt to preflight"
  },
  "vertical": {
   "enum": [
    "software",
    "content",
    "business",
    "education",
    "science",
    "crypto",
    "general",
    "research"
   ],
   "type": "string",
   "default": "general",
   "description": "Domain: software/content/business/education/science/crypto/general/research"
  },
  "endpoint_url": {
   "type": "string",
   "description": "Optional endpoint URL for trust scoring"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pqs-onchainintel-net-4711170a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from pqs.onchainintel.net](https://www.zero.xyz/host/pqs.onchainintel.net/llms.txt)